OT (Sort of) Frame rates

filmy wrote on 1/31/2005, 9:54 PM
Does anyone know if the old 29.97002997002997... issue was ever worked on? I ask because I just loaded up an AE rendered file to my Vegas timeline. Short version is I am doing the dialog edit of a feature - the film was "locked" and sent out, titles were added, effects done and it was "film looked" (Same frame rate - no 24p conversion). So I take it back in and lay it on top - and overall there are about 13 issues with frames being either added or dropped in the "final" version verses the "locked" version.

Than it hit me - the old Vegas method of being "correct" at 29.97002997002997... but AE rendering at 29.97000 exact. Could this be the issue? Something weird was going on. One of the weirdist ones was one edit where the last frame of a shot was perfectly in sync - then the hard cut was right on in both but the frame was off...and this went on for a while - each cut was on the money, but something frame wise was off - than it hit a hard cut and it was off by one frame. So I went back to the last frame of the perfect match and added a "blank frame" and that was what it was - the AE render seems to have dropped a single frame at the edit point. Seems very selective - as in too perfect of a place. And in every case the missing, or added, frames happen right on hard edits. Some on the incoming side, some on the outgoing.

Anyone care to take guesses at this? it would be too simple to say "It dropped a frame on capture" or "just move it one frame" - Nope. Too simple I tell you Stimpy. :)

Comments

Chienworks wrote on 2/1/2005, 4:01 AM
If 29.9700299700299700... vs. 29.9700000000000000 is the issue then the frame sync will only be off once every 9 hours, 16 minutes, 6 seconds, and about 20 frames or so. If you found slipped frames 13 times then either your film is over 120 hours long or something else is causing them.
filmy wrote on 2/1/2005, 6:04 AM
>>>If you found slipped frames...<<<

Not slipped - skipped. Missing...nada.
And also extra - which was part of thie discussion way back when. It was some people found every 88th frame was duplicated. Some found every 5th frame. And yes, there was the every 9 hour one as well. But like I siad things are not that ordered here - it seems more random, and yet these exta frames and missing frames all happen on hard cuts.
John_Cline wrote on 2/1/2005, 7:54 AM
This issue with the different frame rates is basically that at 2 seconds 28 frames from the beginning of each individual 29.97 fps clip, it will repeat a frame. It doesn't matter where the clips are on the timeline.

Here is a link to the original thread from May of 2003. (Note: You-know-who was being "jerkish" in the thread, but otherwise you can see the particulars of the issue.)

http://mediasoftware.sonypictures.com/forums/ShowMessage.asp?ForumID=4&MessageID=179947

You'll see that a forum member named "Brazilian" came to the rescue and wrote a command-line program called "Speedmangler" which changes the header in a 29.97 fps AVI to 29.97002997 for use within Vegas. (It will also do the reverse.) I use it ALL the time and it has been a lifesaver. You can download it from my web site here:

Speedmangler.zip (39k)

And here is the ReadMe file from the Speedmangler program:

-----------------------
SpeedMangler
-----------------------

SpeedMangler attempts to mangle the framerate of an AVI file to the exact framerate of NTSC video, which is actually (30000/1001)fps, or to any framerate you want.

Some other apps mark their NTSC AVIs as 29.97 even, which causes a speed mismatch in other apps that use the more precise framerate calculation and can cause frames to drop or repeat. For example, Adobe's After Effects writes it's movies as 2997/100, whereas Sonic Foundry's Vegas captures and operates at 30000/1001.

SpeedMangler needs to be run from a command prompt (Start Menu -> Programs -> Accessories -> Command Prompt, or use the keyboard Windows Key+R and type "cmd")

Usage: SpeedMangler.exe [filename] [rate] [scale]

[rate] and [scale] are optional arguments to set the rate and scale arbitrarily; If not specified, they default to 30000 and 1001 respectively.

NOTE: Altering the framerate with SpeedMangler does not actually resample the video frames; Drastically changing the framerate will cause audio in the AVI file to no longer be in sync.
JJKizak wrote on 2/1/2005, 7:59 AM
Will it work in XP and 2K?

JJK
John_Cline wrote on 2/1/2005, 8:00 AM
Yes, it works in WinXP and 2k.
filmy wrote on 2/1/2005, 8:24 AM
I had looked at that thread last night and skipped right over this. Doh! Thanks.
Chienworks wrote on 2/1/2005, 8:27 AM
Slipped, skipped, missing, duplicated ... whatever, it doesn't matter. If it was due to the frame rate mismatch there would only be one frame affected every 9+ hours. If you're seeing more than that, it's not due to the frame rate mismatch.
nickle wrote on 2/1/2005, 9:23 AM
If there is a duplicated 88th frame on importing from AE couldn't there just be a script to delete every 88th frame for the imported clip?
John_Cline wrote on 2/1/2005, 9:41 AM
Chienworks,

If he had multiple clips on the timeline each rendered with After Effects, he would be seeing a repeated frame at 2:28 from the beginning of each clip. So it is quite possible to see affected frames randomly throughout the piece.

Nickle,

Curiously, you can't just delete the 88th frame, that doesn't work. The best remedy is using Speedmangler, or render a few seconds of black at the head of the clip in After Effects (or any other program that uses 29.97 even) and then trim the head of the clip to start after 2:28. After it repeats the frame at 2:28, it won't do it for around 6 hours into a single clip.

John
John_Cline wrote on 2/1/2005, 3:58 PM
One more thing, this is a problem that affects everyone that captures or processes video outside of Vegas, whether it's media generated in After Effects or processed with something like Virtual Dub or captured with something like Scenalyzer. If you use any of this media from the beginning, there will be a repeated frame at 2 seconds 28 frames into the clip when you bring it back into Vegas. If you only use a portion of the clip which comes after 2:28, then it's not a problem. It also won't be a problem if you run Speedmangler on it and set it to 29.97002997 fps.

John